OSLO, Norway (AP) — Voters across Norway cast ballots Monday in a parliamentary election that could see a strong showing for the anti-immigration Progress Party and lead to a change of power in the oil-rich nation for the first time since 2005.

Despite Norway’s strong economy and low unemployment, Prime Minister Jens Stoltenberg’s center-left coalition has been trailing in opinion polls for months. The Progress Party appears likely to come into the government for the first time as part of a center-right coalition led by Erna Solberg’s Conservative Party, which pledges to increase the availability of private health care and cut wealth taxes on assets over $140,000.

The discovery of oil and gas in Norway’s waters in the 1960s turned the Scandinavian nation into one of the richest in the world, with a strong welfare system and a high living standard. The oil helped Norway withstand Europe’s financial crisis and has allowed it to create an investment fund for the country’s future that is now worth around $750 billion.

One political expert said Stoltenberg’s main challenge Monday was simply that he had been in power for so long.

“I call it government fatigue. The Labor coalition has been in power for eight years and one would expect that some voters now think it is time for a change,” said Frank Aarebrot, professor of comparative politics at the University of Bergen.

This is the first parliamentary election since Anders Behring Breivik killed 77 people in 2011. Thirty-three survivors of the massacre on Utoya island, mostly teen members of the Labor Party youth wing, are seeking national office in the election.

Stoltenberg was admired for his calm demeanor after the 2011 terror acts and there was a short-lived boost in support for his Labor Party. But last year a report criticizing Norwegian police for a litany of institutional failures before and during the attacks dented his government’s prestige.